CVE-2026-27826 MCP Atlassian has SSRF via unvalidated X-Atlassian-Jira-Url / X-Atlassian-Confluence-Url headers

What is CVE-2026-27826?

CVE-2026-27826 is a high-severity server-side request forgery vulnerability in sooperset mcp-atlassian, published on 10 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to version 0.17.0, an unauthenticated attacker who can reach the mcp-atlassian HTTP endpoint can force the server process to make outbound HTTP requests to an arbitrary attacker-controlled URL by supplying two custom HTTP headers without an `Authorization` header. No authentication is required. The vulnerability exists in the HTTP middleware and dependency injection layer — not in any MCP tool handler - making it invisible to tool-level code analysis. In cloud deployments, this could enable theft of IAM role credentials via the instance metadata endpoint (`169[.]254[.]169[.]254`). In any HTTP deployment it enables internal network reconnaissance and injection of attacker-controlled content into LLM tool results. Version 0.17.0 fixes the issue.

Weakness: CWE-918

Which versions are affected by CVE-2026-27826?

3 open source packages ship an affected version, including mcp-atlassian. It affects 1 product.

Products include Sooperset Mcp Atlassian.

How do I fix CVE-2026-27826?

Upgrade mcp-atlassian to 0.17.0 or later.

Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.

Is CVE-2026-27826 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27826 exists.

Public exploit code: 1 Nuclei template.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-7r34-79r5-rcc9, PYSEC-2026-2621.